Destruction of Salmonella enteritidis inoculated in liquid whole egg by high hydrostatic pressure: Comparative study in selective and non-selective media

The destruction of Salmonella enteritidis inoculated in liquid whole egg at approximately 10⁷-10⁸ cfu ml^-1 was studied under combinations of pressure (350 and 450 MPa), temperature (50, 20, 2 and - 15°C) and time (5, 10, 15 min and cycles of 5 + 5 and 5 + 5 + 5 min). One non-selective medium (tryptone soy agar) and two selective media (brilliant green agar and salmonella-shigella) were used to evaluate viability of S. enteritidis after pressurization. The inactivation rate increased with pressure and exposure time, being minimal at 350 MPa and - 15°C for 5 min (over 1 log₁₀ of reduction) and reaching total inactivation (8 log₁₀ of reduction) in several treatments at 50°C. Treatments in cycles showed greater effectiveness than continuous treatments of the same total time. The effect of pressure was enhanced by elevated temperatures. The higher counts were obtained in the non-selective medium, indicating the presence of injured cells after pressure treatment. D-values obtained for two temperatures (2 and 20°C) and different times (0-60 min) under controlled pressure (400 MPa) showed that microbial inactivation followed a first-order kinetics with a decimal reduction time evaluated in tryptone soy agar medium of 9.5 min at 2°C and 8.8 min at 20°C.